it varies how much lintel (the header over the window) you need, it's determined by the size of the window/width of concrete/rebar, etc... You should have no problem, well, it'll be a little problem, moving the window.. it's possible that a heavy metal support may have to be fastened above because it sounds like you'll be removing structural rebar from above the window. The gap on the bottom could easily just be framed in..
Think about this.. .egress windows are added into concrete basements all the time.

If there is ANY possibility the basement room will be used for a bedroom, or if that is the only window in the basement, then it is an egress window. The sill has to be no more than 44" above the floor. Also, since you're looking to move it up, you're creating a potential leak problem if you don't get the area below it sealed really well. I think you'd be better off to consider cutting out the upper portion and installing a taller window. Cutting it out ain't gonna be easy, but it can be done. However, make sure you retain adequate lintel strength and reinforcement above the window. If this is just a basement wall, i.e. no ICF wall above, that probably isn't a problem.

Here's the pertinent words from the 2006 IRC. Double check to see if the IRC applies to your jurisdiction. Most likely whatever code you're under, this requirement does apply.

SECTION R310
EMERGENCY ESCAPE AND RESCUE OPENINGS
R310.1 Emergency escape and rescue required. Basements
and every sleeping room shall have at least one operable emergency
and rescue opening. Such opening shall open directly
into a public street, public alley, yard or court. Where basements
contain one or more sleeping rooms, emergency egress
and rescue openings shall be required in each sleeping room,
but shall not be required in adjoining areas of the basement.
Where emergency escape and rescue openings are provided
they shall have a sill height of not more than 44 inches (1118
mm) above the floor.